<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>z-index的讲解</title>
	<style type="text/css">
		.a{
			position: relative;
			width: 200px;
			height: 40px;
			background-color: #C3FFFB;
			border: 3px solid #3962FE;
			z-index: 1;

		}
		.b{
			position: relative;
			width: 200px;
			height: 40px;
			background-color: #C3FFFB;
			border: 3px solid #3962FE;
			top: -30px;
			left: 50px;
			z-index: 10000;

		}
		.c{
			position: relative;
			width: 200px;
			height: 40px;
			background-color: #C3FFFB;
			border: 3px solid #3962FE;
			top: -50px;
			left: 100px;
			/*z-index: auto;*/
			z-index:10;
		}
	</style>
</head>
<body>
	<div style="position: relative;z-index: 15;">
		<div class="a">A</div>
	</div>
	
	<div style="position: relative;z-index: 10;">
		<div class="b">B</div>
	</div>
	<div class="c">C</div>
</body>
</html>